Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$192.57	12.842%	$217.2998	$217.30	$217.30	$217.30
Purchase #2	$61.92	7.548%	$66.5937	$66.59	$66.60	$66.60
Purchase #3	$156.37	6.580%	$166.6591	$166.66	$166.65	$166.70
Purchase #4	$196.66	11.420%	$219.1186	$219.12	$219.10	$219.10
Purchase #5	$187.81	11.840%	$210.0467	$210.05	$210.05	$210.00
Purchase #6	$42.38	3.155%	$43.7171	$43.72	$43.70	$43.70
Purchase #7	$70.71	10.586%	$78.1954	$78.20	$78.20	$78.20
7 purchase totals =	$908.42		$1,001.6304	$1,001.64	$1,001.60	$1,001.60